Deduplicate dat files that are the 'same'

[LeftofZen]

There are many dat files with the same names, near-identical data, and close file edit/create dates. These appear to be different versions of the same file over time, and can essentially be counted as the 'same' file. We should set up an automated process to at the very least display these duplicates together, and then perhaps allow some kind of merging, or showing the latest file. It will probably be important to store all versions in the database so they can be marked as 'known' if they're discovered by a user.